As you can see from my pics, I did that today. I am a woman and have small hands, could not get to the faucet nuts to tighten. Luckily it did not need tightening but I just wondered if it did. Would have to get a wrench up there to turn it. As to the black tank back flow preventer valve, I just learned of this and will order the part to have on hand it seems fine now. But you did not put in a new valve, just a 90 degree elbow?